The invention, in some embodiments thereof, relates to a method of attaching a molecule-of-interest to a microtube and, more particularly, but not exclusively, to electrospun microtubes including the molecule-of-interest attached thereto.
In nature there is an enormous variety of enzymes that catalyze reactions, some of which have industrial use. These include oxidoreductases, transferases, hydrolases, lyases, isomerases, and ligases. Immobilization of enzymes on solid substrates sometimes offers advantages over the use of a free enzyme. For example, immobilization can stabilize enzymes, enable better control of enzymatic reactions, allow the reuse of the enzyme and prevent enzyme loss with time. The material bearing the immobilized enzyme has a significant role in evoking these advantages both from architectural and chemical points of view.
Nanofibers and polymeric nanofibers in particular can be produced by an electrospinning process (Reneker D H., et al., 2006; Ramakrishna S., et al., 2005; Li D., et al., 2004; PCT WO 2006/106506 to the present inventors). Electrospun polymeric nanofibers have been widely used in biological applications such as scaffolds, carriers for biologically active molecules like proteins and enzymes (Xie J., et al., 2003; Zhang Y Z., et al., 2006; Jiang H., et al., 2006; and Patel A C., et al., 2006) and encapsulation of viruses and bacteria (Salalha W., et al., 2006).
Several approaches can be used to entrap or attach enzymes to electrospun fibers. One approach is to immobilize the enzyme on the outer surface of the nanofibers by either covalently attaching the desired enzyme to the functional groups of the polymer surface (Ye P., et al., 2006; Jia H., et al., 2002; Kim T G., et al., 2006) or physically absorbing the enzyme to the surface (Huang X J., et al., 2006). The second approach, which results in encapsulation of enzymes, is based on mixing the enzyme with the polymer solution prior to the electrospinning process (Xie J. and Hsieh Y-L, 2003). However, encapsulation is often associated with leaching of the enzymes, e.g., via fiber dissolution and burst releases (Zhang Y Z., et al., 2006), especially, when the host polymer is a water soluble polymer such as poly(vinyl alcohol) (PVA) or dextran. To prevent immediate dissolution of the fibers in a physiological environment (e.g., blood) and the subsequent enzyme leaching, the electrospun fibers can be crosslinked by chemical or physical agents such as glutaraldehyde or UV irradiation. Alternatively Zeng J, et al. (2005) suggested that PVA fibers can be coated with water insoluble polymers using a chemical vapor deposition (CVD). However, the organic solvents of the water insoluble polymers are harmful to biological material and can lead to loss of enzymatic activity. To overcome this problem, Herricks et al. (2005) suggested to use surfactant-stabilized enzymes in an organic solution of polystyrene (PS) as a spinning solution. In this way the electrospun nanofibers are insoluble in water and the enzymatic activity is retained due to surfactant stabilization (Herricks T E., et al., 2005).
Sun and co-workers (Sun Z, et al., 2003) describe the production of core-shell nanofibers (i.e., filled fibers) by co-electrospinning of two polymeric solutions using a two co-axial capillaries spinneret. US patent application No. 20060119015 to Wehrspohn R., et al. describes the production of hollow fibers by introducing a liquid containing a polymer to a porous template material, and removal of the template following polymer solidification. PCT/IB/2007/054001 to the present inventors (which is fully incorporated herein by reference) discloses methods of producing electrospun microtubes (i.e., hollow fibers) which can be further filled with liquids and be used as microfluidics.